I don't know about finding the old rulebook, but I've had two clubrally cars grandfathered into the current ruleset so I'm somewhat familiar with what the standards used to be and how that translates to the current sanctioning bodies, as are some others here. What did you want to know?

Nothing specific, but one of my projects is a "historic" SCCA rally car which I am trying to restore back to its former glory (within reason). That being said, since it's kind of a clean slate with most of the original parts missing, I'm willing to take some liberties. In this article, the "SCCA limit of 389 cubic inches" stuck out to me, so I'm a little curious what a ragged edge of the rule book build would look like...

I believe the displacement adjustment chart hasn't changed much, if at all, so for Group 5 you have a maximum of 5100cc with a multiplier of 0.8 for pushrod engines, so up to 6375cc if you keep it pushrod and N/A. You could do whatever you want to the internals within that displacement.

Got THAT right. I had one in my autocross SHO, then transplanted it to my STI, both with coilovers, and long distances were NOT fun. Bought some extra pillows but that still didn't make it anywhere near "comfortable".

The time I thought about adding light coil-overs to my Fairmont, and keeping springs in the factory location, I got laughed at and people shook their heads. I'm glad I wasn't the idiot everyone thought I was. I never did do it, but at least it wasn't a bad idea.